Making Your Houseplants Chirp When They're Thirsty

Sometimes I think it might be nice if a few of my houseplants would just tell me when they need a drink.

I have a plethora of plants in my house. They all have different watering schedules, but like many people, I'm a creature of habit.

The plants that need watering daily or every other day are taken care of, but those that need water on a more varied schedule can often get overlooked. Chirp sets out to remedy this with a simple alarm.

The Chirp alarm is a small pcb that is inserted into the soil at its driest desired point. From that moment forward it monitors the soil and begins to sound an alarm when the soil reaches the preset dry point. It begins with a quiet chirp, getting more urgent over time. However, it is nice enough to silence itself at night by detecting light levels. The developers note that the battery, a single button cell, can last roughly a year depending on how often it chirps and the light sensors are used. If you keep your plants watered, the battery lasts longer.

One interesting aspect of the chirp is that it is uses capacitive humidity sensing. A capacitive sensor doesn't require physical contact so it can be coated to help prevent corrosion. If you would like to read details about how exactly the capacitive sensing works, the developer has written a nicely detailed article on it here. The rest of the hardware is pretty simple. The device uses a ATTiny44a with a standard AVR 6 pin ISP programming header, allowing for customizing your modifications. This ISP header is also there so that another device can be used to read the data, should a user want to incorporate the Chirp into a larger project.

This project is entirely open-source and even comes with downloadable code. A gallery of images is posted on the website, showing the various prototypes the designers iterated on before landing on final design. One amusing thing to point out: Chirp actually began as a joke. Some people say there is a grain of truth to the best jokes, so with that in mind, the Chirp was born.

These things have been around since time immemorial, usually variations on a 555 with the trigger pin held low by damp earth, when the earth dries out it starts oscillating. Clever idea to use capacitive sensing so you don't get electrolysis though. With a uC you can do all sorts of clever stuff like check for overwatering as well. Re Battery life, being as this is a long-term monitor, you could shut the uC down and just check the dampness every 15 minutes or even every hour, and then only if there is light on it.You could probably monitor for frost as well (Geraniums don't like that...)

So kudos to the designers for coming up with a clever new take on an old idea.

My husband and I were having a miserable experience this year with geraniums in our windowboxes, something that had always been reliably easy for us. We were wondering, "Is it too hot? Are they not blooming because we just bought weakling plants?" We were away for a couple of days and when we came back the geraniums were in beginning to bud. Apparently, my husband had been overwatering them. Seems that this device could be programmed to also check for waterlogged soil.

I think you've got something there, Janine. A chirp or an electric shock when reaching for cake. It's beginning to sound like that Star Trek episode...you know, the one where they're wearing those collars, and ....

Not sure how I feel abou this. On the one hand, I think it is really cool and it would help me prevent killing houseplants (I'm quite good at it). On the other hand, that chirping seems really annoying. Although, i guess if I JUST watered the plants.... OK, so this is good for behavior modification. Maybe i can also get something that shrieks when I cut a piece of cake...Or maybe my treadmill can holler out in pain when I haven't used it in days....